Various types of electronic units are mounted on a motor car as a moving body. The motor car is provided with wire harnesses for the purpose of transmitting electric power from a power source, and control signals and so on from a computer or the like to the electronic units. Each of the wire harnesses includes a plurality of electric wires, and a plurality of connectors to be attached to ends of the electric wires.
The electric wire is composed of an electrically conductive core wire and a sheath made of insulating synthetic resin for covering the core wire. The electric wire is a so-called sheathed wire. The connector is provided with electrically conductive terminal metals and an insulating connector housing. The terminal metals are fixed to the ends of the electric wires so as to be electrically connected with the core wires of the electric wires. The connector housing is formed in a box-like shape and contains the terminal metals.
On occasion of assembling the above described wire harness, the electric wires are cut into a predetermined length as a first step, and then, the terminal metals are fixed to the ends of the electric wires. A plurality of the electric wires are connected to each other, according to necessity. Thereafter, the terminal metals are inserted into the connector housing. The wire harness can be assembled in this manner.
It is necessary to identify the electric wires of the above described wire harness with respect to a size of the core wire, material of the sheath (the material may vary depending on presence of heat resisting property or so), an object for use, etc. The object for use means, for example, an air bag, an ABS (Antilock Brake System), a power transmitting system, and a system of the motor car in which the electric wires for transmitting control signals including vehicle speed information etc. are employed.
Conventionally, the electric wire for the wire harness has been provided with a ring-like band mark in a part of its outer face along an entire circumference thereof, in order to identify the objects for use (systems), as described above. For this purpose, it has been conventionally accustomed that when synthetic resin is extruded to form the sheath around the core wire, coloring agent of a desired color is admixed to the synthetic resin. Then, another coloring agent which has different color from the aforesaid coloring agent is applied to a part of the synthetic resin which has covered the core wire, that is, the outer face of the sheath, along an entire circumference thereof. In this manner, the part of the outer face of the sheath has been colored along the entire circumference thereof to form the band mark on the electric wire.
In a process for forming the band mark on the above described electric wire, the coloring agent has been applied to the outer face of the electric wire by blowing it together with a pressurized air, as an aerosol. On this occasion, a plurality of nozzles have been employed for blowing the coloring agents, and these nozzles have been arranged along a circumferential direction of the electric wire at a substantially equal interval.
A plurality of the nozzles have been conventionally employed as described above. Therefore, there has been such a problem that an apparatus for marking the electric wire has become large-sized requiring a larger space for installation, and that a production cost for the apparatus has been increased. This would incur a rise of the overall cost for marking the electric wire.
In view of the above, an object of the present invention is to provide a method and an apparatus for marking an electric wire which can be offered at a low cost.